/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.io;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.net.URL;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.StandardOpenOption;

import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * {@link Resource} implementation for {@code java.io.File} handles.
 * Supports resolution as a {@code File} and also as a {@code URL}.
 * Implements the extended {@link WritableResource} interface.
 *
 * <p>Note: As of Spring Framework 5.0, this {@link Resource} implementation
 * uses NIO.2 API for read/write interactions. Nevertheless, in contrast to
 * {@link PathResource}, it primarily manages a {@code java.io.File} handle.
 *
 * @author Juergen Hoeller
 * @see PathResource
 * @see java.io.File
 * @see java.nio.file.Files
 * @since 28.12.2003
 */
public class FileSystemResource extends AbstractResource implements WritableResource {

    private final File file;

    private final String path;


    /**
     * Create a new {@code FileSystemResource} from a {@link File} handle.
     * <p>Note: When building relative resources via {@link #createRelative},
     * the relative path will apply <i>at the same directory level</i>:
     * e.g. new File("C:/dir1"), relative path "dir2" -> "C:/dir2"!
     * If you prefer to have relative paths built underneath the given root
     * directory, use the {@link #FileSystemResource(String) constructor with a file path}
     * to append a trailing slash to the root path: "C:/dir1/", which
     * indicates this directory as root for all relative paths.
     *
     * @param file a File handle
     */
    public FileSystemResource(File file) {
        Assert.notNull(file, "File must not be null");
        this.file = file;
        this.path = StringUtils.cleanPath(file.getPath());
    }

    /**
     * Create a new {@code FileSystemResource} from a file path.
     * <p>Note: When building relative resources via {@link #createRelative},
     * it makes a difference whether the specified resource base path here
     * ends with a slash or not. In the case of "C:/dir1/", relative paths
     * will be built underneath that root: e.g. relative path "dir2" ->
     * "C:/dir1/dir2". In the case of "C:/dir1", relative paths will apply
     * at the same directory level: relative path "dir2" -> "C:/dir2".
     *
     * @param path a file path
     */
    public FileSystemResource(String path) {
        Assert.notNull(path, "Path must not be null");
        this.file = new File(path);
        this.path = StringUtils.cleanPath(path);
    }


    /**
     * Return the file path for this resource.
     */
    public final String getPath() {
        return this.path;
    }

    /**
     * This implementation returns whether the underlying file exists.
     *
     * @see java.io.File#exists()
     */
    @Override
    public boolean exists() {
        return this.file.exists();
    }

    /**
     * This implementation checks whether the underlying file is marked as readable
     * (and corresponds to an actual file with content, not to a directory).
     *
     * @see java.io.File#canRead()
     * @see java.io.File#isDirectory()
     */
    @Override
    public boolean isReadable() {
        return (this.file.canRead() && !this.file.isDirectory());
    }

    /**
     * This implementation opens a NIO file stream for the underlying file.
     *
     * @see java.io.FileInputStream
     */
    @Override
    public InputStream getInputStream() throws IOException {
        try {
            return Files.newInputStream(this.file.toPath());
        } catch (NoSuchFileException ex) {
            throw new FileNotFoundException(ex.getMessage());
        }
    }

    /**
     * This implementation checks whether the underlying file is marked as writable
     * (and corresponds to an actual file with content, not to a directory).
     *
     * @see java.io.File#canWrite()
     * @see java.io.File#isDirectory()
     */
    @Override
    public boolean isWritable() {
        return (this.file.canWrite() && !this.file.isDirectory());
    }

    /**
     * This implementation opens a FileOutputStream for the underlying file.
     *
     * @see java.io.FileOutputStream
     */
    @Override
    public OutputStream getOutputStream() throws IOException {
        return Files.newOutputStream(this.file.toPath());
    }

    /**
     * This implementation returns a URL for the underlying file.
     *
     * @see java.io.File#toURI()
     */
    @Override
    public URL getURL() throws IOException {
        return this.file.toURI().toURL();
    }

    /**
     * This implementation returns a URI for the underlying file.
     *
     * @see java.io.File#toURI()
     */
    @Override
    public URI getURI() throws IOException {
        return this.file.toURI();
    }

    /**
     * This implementation always indicates a file.
     */
    @Override
    public boolean isFile() {
        return true;
    }

    /**
     * This implementation returns the underlying File reference.
     */
    @Override
    public File getFile() {
        return this.file;
    }

    /**
     * This implementation opens a FileChannel for the underlying file.
     *
     * @see java.nio.channels.FileChannel
     */
    @Override
    public ReadableByteChannel readableChannel() throws IOException {
        try {
            return FileChannel.open(this.file.toPath(), StandardOpenOption.READ);
        } catch (NoSuchFileException ex) {
            throw new FileNotFoundException(ex.getMessage());
        }
    }

    /**
     * This implementation opens a FileChannel for the underlying file.
     *
     * @see java.nio.channels.FileChannel
     */
    @Override
    public WritableByteChannel writableChannel() throws IOException {
        return FileChannel.open(this.file.toPath(), StandardOpenOption.WRITE);
    }

    /**
     * This implementation returns the underlying File's length.
     */
    @Override
    public long contentLength() throws IOException {
        return this.file.length();
    }

    /**
     * This implementation creates a FileSystemResource, applying the given path
     * relative to the path of the underlying file of this resource descriptor.
     *
     * @see org.springframework.util.StringUtils#applyRelativePath(String, String)
     */
    @Override
    public Resource createRelative(String relativePath) {
        String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
        return new FileSystemResource(pathToUse);
    }

    /**
     * This implementation returns the name of the file.
     *
     * @see java.io.File#getName()
     */
    @Override
    public String getFilename() {
        return this.file.getName();
    }

    /**
     * This implementation returns a description that includes the absolute
     * path of the file.
     *
     * @see java.io.File#getAbsolutePath()
     */
    @Override
    public String getDescription() {
        return "file [" + this.file.getAbsolutePath() + "]";
    }


    /**
     * This implementation compares the underlying File references.
     */
    @Override
    public boolean equals(Object obj) {
        return (obj == this ||
                (obj instanceof FileSystemResource && this.path.equals(((FileSystemResource) obj).path)));
    }

    /**
     * This implementation returns the hash code of the underlying File reference.
     */
    @Override
    public int hashCode() {
        return this.path.hashCode();
    }

}
